The efficiency with which light is transmitted from the end of one optical fiber to another is directly dependent upon, among other things, the concentric alignment of the fiber ends with one another and the medium, dirt or other light dispersive materials which come between the ends of the fiber and through which light must be transmitted. In addition, preparation of fiber ends is important. See for example, "Low Loss Splicing and Connection of Optical Waveguide Cables" by Robert M. Hawk and Frank L. Thiel, SPIE, Vol. 63 (1975) and "A Fiber-Optic-Cable Connector" by C. M. Miller, The Bell System Technical Journal, November 1975.
Prior art fiber optic connectors are generally designed such that fibers slide into a tube-like receiver, abutting end-to-end somewhere near the middle therein. In these designs, fibers tend to push dirt ahead at the fiber end causing interference. To clean that dirt out of a small aperture is very difficult. In addition, fiber ends may be damaged by the dirt or during the cleaning process, or they may fracture when they contact one another at the center of the tube.
The present invention achieves high tolerance concentricity for fibers as small as 0.002 inches O.D. by utilizing two half-shells having milled or broached flat surfaces and small radius for retaining the fiber. The half-shells are pressfit into a retainer sleeve to form the ferrule assembly. Close concentricity tolerances of inside and outside diameters are held and can be adjusted by an adjustable broach blade.
To join the ferrule to the optical fiber, fiber jacket is stripped away from the fiber, the fiber end is cleaved square and inserted between the two half-shells with the end of the fiber flush with ends of the half-shells which are then retained by the sleeve. After the ferrule and fiber have been assembled, the rear portion of the retainer sleeve of the ferrule is crimped to the jacket. The connector of the two fibers to be connected, each of which include a boot and shoulder nut, is then inserted into each end of a split, outside-threaded sleeve and retained therein by the shoulder nuts.
The connector of this invention provides better alignment of fiber-to-fiber ends for maximum light transmission. The closer two fiber ends can be aligned on their common centerline, the less light or power is lost. The connector can be assembled and disassembled many times with no injury to the fiber, since the fiber end is completely protected by the ferrule. The fiber end can be cleaned and inspected conveniently without removing the fiber from the ferrule since the fiber end is visible at interface end of the ferrule. Ferrule concentricity is controlled by machining identical halves which are assembled by interference fit into the retainer sleeve. The sleeve can be any size and shape to accept various cable jackets. Since the small I.D. for retaining the fiber is formed by broaching two halves of the ferrule half-shells, the problems of drilling very small holes, i.e., the near impossibility of drilling truly round holes of very small diameters, are not encountered.